I install ZFS on root just like in Andrew ZFSOnRoot wiki page.
I don't use legacy mount points.

I also set "atime=off" on tank and all partitions inherit it from tank.
When I reboot after install, root file system is mounted with atime option:
# zfs get atime tank
NAME PROPERTY VALUE SOURCE
tank atime on temporary

I can fix this with creating entry in fstab for root fs with noatime,
but maybe there is some way how to pass options to vfs.root.mountfrom?